“I was using all the time and I couldn’t wake up and go to class,” he told CTVNews.ca. “It was every day, multiple times a day, as much as I could afford to.”

He’d experienced his first bout of hallucinations when he smoked a joint at age 13, what he now considers “foreshadowing” of later episodes. At university, mood changes and worsening depression, a condition he’d already dealt with for much of his life, became confounded by other symptoms. He experienced what is known as “delusions of reference,” when a neutral event or coincidence is believed to have personal significance.

“One time I saw a cop car across the street and immediately thought ‘The police are coming after me. I’m going to jail,’” he recalled, adding that he was sober at the time. “(Cannabis) kind of triggered something as far as I could tell.”

After a suicide attempt brought Khamis to the hospital, he received the general diagnosis of psychosis, a symptom of several mental illnesses, including schizophrenia, in which people have difficulty distinguishing between what is real and what is not. Though much research is still needed in the area of cannabis-induced psychosis, Khamis has since stopped using the drug and works as a peer counsellor for people with psychosis. On Wednesday, he joined Dr. Robert Zipursky, a scientific adviser for the Schizophrenia Society of Ontario, on CTV’s Your Morning to bring awareness to the issue. Recent figures from the Canadian Institute for Health Information suggest there has been a steady rise in cannabis-induced psychosis in recent years. While there is more research to be done, Zipursky said the links between cannabis and psychosis are becoming more clear.

“We don’t exactly know who’s vulnerable. It seems like all of us are vulnerable,” he said, but some people seem to be at “increased risk.”

Those subgroups include people with family history of schizophrenia or bipolar disorder, those who use cannabis on a daily basis, and people who use high-potency forms of cannabis. Studies have shown that cannabis use can lead to acute psychosis that may dissipate within a few weeks, he said, but those who have experienced acute psychosis are at increased risk of developing schizophrenia.

“People who develop an acute psychosis with cannabis have about a 50 per cent chance of ending up with schizophrenia in the long run,” he said on Your Morning.

The precise science of it all is still uncertain, Zipursky added. “How that actually happens we’re not clear about. There is some early research showing that there may be some brain changes.” Young people who have used cannabis have exhibited some evidence of cognitive changes related to memory and attention, which Zipursky said points to “negative effects on the actual substance of the brain.”

Khamis, who has received varying diagnoses including schizoaffective disorder, said his health has improved greatly since adopting a self-care routine and taking medications. He’s also very much in favour of the recent legalization of recreational cannabis use in Canada.

“I’m fully on board. I think that having an open conversation around it where it’s not stigmatized is a big thing,” he said. “This opens up a pathway to more research.”